These efforts are laudable. But these actions demonstrate that policymakers see mitigation and adaptation as mutually exclusive. That's a mistake.

Sometimes, even successful efforts to mitigate climate change can lead to more local warming. And climate change could render the most forward-thinking adaptation efforts obsolete.

To ensure that cities remain livable, mayors and urban leaders - together with urban designers - must simultaneously cut emissions and help residents adapt to a warming planet.

Consider the push to boost the number of energy-efficient buildings. Such efforts are only successful if planners also keep cityscapes cool, as efficiency doesn't always reduce energy use.

In Hong Kong, for example, a series of tall, wall-like buildings have blocked the flow of air.

By cutting off a natural source of cool air, these buildings have increased local temperatures and thus lifted demand for air-conditioning, even in the city's newest, most energy-efficient buildings.

Or look at the drive to increase population density in urban centers. Such moves reduce emissions since people can forego automobiles and tend to like public green space.

But dense urban areas also tend to contain lots of heat-absorbing materials like asphalt. That can make them much hotter than their surroundings.

This "heat island effect" can leave city residents with little choice but to crank up their air conditioning and, consequently, increase emissions.

Focusing exclusively on adaptation, meanwhile, is short-sighted. The climate will continue changing, and the longterm impact of climate change will be too severe to manage by simply adapting.

Cities that embrace "adaptive mitigation" - those that reduce CO2 emissions while also helping their residents adapt to a changing climate - are better positioned to remain livable.

Again, take density. Smart cities intersperse green spaces and parks throughout building-heavy, highly populated areas. This vegetation absorbs harmful air pollutants. One tree can absorb as much as 26 pounds of CO2 in a year.

The shade provided by trees can also help lower temperatures. Further, water vapor evaporating from plant surfaces cools the surrounding air.

Glasgow, Scotland, has increased its green areas by 20 percent. Consequently, the city is poised to cut its urban heat island effect in half by 2050.

Similarly, pedestrian and cycling corridors can reduce emissions and cool cities through extra ventilation and shade.

Such climate strategies don't require expensive technologies or sustained political will. Yet they're often overlooked when city leaders focus exclusively on carbon emissions or adaptation.

Two-thirds of the world's population will live in cities by 2050. Most of the urban spaces these individuals will inhabit have yet to be designed. So the design decisions we make today will have extraordinary consequences on our climate for generations.

But they'll also affect the culture of the planet's growing urban population. As mayors and urban leaders plan for a warming planet, they shouldn't forget that, above all, cities are for living.

Jeffrey Raven is director of the Graduate Program in Urban and Regional Design at New York Institute of Technology.